WASHINGTON (CNN) -- While U.S. citizens will be required to show proof of identification and citizenship at land and sea borders beginning January 31, the truly big changes will occur in June of 2009 when more stringent requirements take effect.

At that point, citizens returning to the United States via land and sea will be required to carry passports, just as they are required to when arriving via air today.

But there is an alternative. The Department of Homeland Security has approved a number of alternatives for frequent border crossers.

First, DHS is working with numerous border states to develop "enhanced drivers' licenses" that would meet government security requirements and be accepted at border crossings. Washington state's first enhanced license should be issued later this month. Vermont, New York and Arizona also have signed agreements with DHS, and other states are in discussions, said Kelly Klundt of the Customs and Border Protection.

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The State Department is also developing a passport card -- a wallet-sized card that would be cheaper and more convenient than a passport, but would fulfill the same function at land borders.

Passport cards and enhanced drivers' licenses both will have "vicinity radio frequency identification," or RFID, chips, which will identify the holders as they approach border checkpoints.

Klundt says the chips will not transmit sensitive information. They will only contain a unique number that the CBP can use to automatically call up information on the travelers and query law enforcement databases.

"You are at no greater risk of identity theft using an RFID than if someone snagged your library card or your license plate," Klundt said. "There's nothing on the card other than a unique number that's a combination of zeros and ones."

The number is useless to anyone who doesn't have access to the government databases, she said.

The automatic nature of the readers will limit the data entry job of border officials, giving them more time to interact with the travelers, Klundt said.

Blaine, Washington, and Nogales, Arizona will be the first to get border card readers, which should be installed in mid-February, she said. The State Department is expected to issue the first passport cards this spring.E-mail to a friend